News · BA111OD

BA111OD shrinks the CHPTR_Δ to 40 mm without losing its triangular hours

The Swiss maker puts its hypocycloidal hour display into a smaller steel case, with 30 watches planned and availability from late October.

Hen & Mills Editorial · 4 min read · 1 October 2026

• BA111OD has reduced its existing CHPTR_Δ hour-display watch from 44 mm to 40 mm while keeping the triangular path of its yellow hour marker.
• The steel case houses a Soprod M100 automatic base with BA111OD’s 09310 hypocycloidal module, under a domed sapphire crystal.
• Production is a single run of 30 unnumbered pieces, due at the end of October, priced at CHF 2,800 in Switzerland.

The dial of a conventional watch makes the hour hand trace a circle. BA111OD's Chapter Delta takes a less direct route: a yellow marker travels around a softly curved triangle while a separate hand reads the minutes. That display was already part of the brand's 44 mm CHPTR_Δ. The news announced on 25 September is a change in proportion, with the same unusual reading of time brought into the CHPTR_Δ [MdP] 40 mm.

A smaller case around the same triangular display

Reducing a case from 44 mm to 40 mm sounds simple until the dial has a moving display that needs room to explain itself. Here, the steel triangle remains the organising feature, while the yellow point marks the hour along its mechanically determined path. BA111OD says the intention was to preserve the original complication's character in a more compact watch. This is a new size for an existing idea, rather than a claim to have invented a new way of telling time this September.

The 316L stainless steel case measures 40 mm across and 12.9 mm thick, with a crown at four o'clock. BA111OD fits a domed sapphire crystal with antireflective treatment over the dial, a sapphire display back and a water-resistance rating of 5 ATM. It does not publish a lug-to-lug figure on the product page, so diameter and thickness are the available measurements. Those numbers establish the extent of the reduction without pretending to tell us exactly how the watch sits on a wrist we have not tried.

Under the crystal, a satin-matt steel dial is built in several levels with blue accents and laser engraving. The polished steel triangle frames the mechanism at its centre, rather than covering it with a printed motif. A conventional minute hand and the yellow hour dot do different jobs; BA111OD specifies Super-LumiNova for the indication. The design asks the wearer to learn one extra visual rule, but it gives that rule a visible mechanical cause. The triangle is the hour marker's route, not just an outline applied for effect.

What drives the yellow point

BA111OD calls the display hypocycloidal, referring to the geometry that guides the hour indication around the dial. Its 09310 module sits on a Soprod M100 automatic base. The brand says the complication was developed with watchmaker Olivier Mory at BCP Tourbillons in La Chaux-de-Fonds; BA111OD acquired BCP in 2026 and now describes that movement work as part of its LAB 11:10. Design and assembly take place in Neuchâtel. These are the brand's stated production roles, rather than a claim that every movement component is made in-house.

The movement has 25 jewels and a stated power reserve of 42 hours. From the back, the sapphire window reveals the automatic base movement, while the dial side is where the uncommon display earns its place. A decorative openwork dial can show a great deal without changing how its owner reads the time; this one makes the mechanism responsible for the reading itself. Whether that extra step feels engaging or inconvenient is a matter of taste, and a press image cannot settle it.

Each watch is supplied on a blue rubber strap with a double-folding deployant clasp. BA111OD also offers a stainless steel bracelet version, and its Club 11:10 members receive a complimentary steel bracelet with a purchase. The brand says both the rubber strap and bracelet use its Easy Clip system. The blue strap gives the steel and blue dial a coherent palette, while the bracelet offers a different finish without asking an owner to keep a second watch for it. The complimentary bracelet is tied to club membership, rather than every order.

Thirty pieces, but not a numbered edition

BA111OD says it will make the 40 mm CHPTR_Δ [MdP] once, in a run of 30 pieces. It explicitly does not present the watch as a numbered limited edition. A single production run places a real limit on supply, but it does not promise an individual edition number on each case. The brand's 25 September announcement positions the run as a way to introduce its existing complication in new proportions. Nothing in the published material suggests a permanent 40 mm Delta range will follow.

The smaller format makes the watch easier to consider for people who liked the original display but found a 44 mm case too much on paper. It does not remove the design's deliberate strangeness, and it should not. The separate circular minute hand and triangular hour route are the point of this watch. BA111OD has changed the amount of case around them, which is a more interesting decision than merely scaling down a conventional dial.

CHPTR_Δ [MdP] 40 mm pricing and availability

BA111OD lists the watch at CHF 2,800 in Switzerland. Its Australian storefront quotes US$4,055, without an Australian-dollar price; the United States storefront lists US$4,100 and says its displayed US prices include tariffs. The brand gives the end of October 2026 as the availability timing. Production is a one-off run of 30 pieces, with the additional steel bracelet complimentary to Club 11:10 members. Australian-dollar pricing has not been published.